This how-to supposes that the downloaded file is saved in the “Downloads” directory situated in your home directory.

2. Extract

The downloaded file is a compressed .tar.bz2 archive. To extract this juicy archive, open the Downloads directory. Look for a file named firefox-15.0.tar.bz2, right-click on it and select “extract here”.

Alternatively, you can extract the archive from the command line:cd ~/Downloads/tar xjf firefox-15.0.tar.bz2

For those interested, here are the tar arguments used in the command:x : eXtractj : deal with bzipped filef : read from a file (rather than a tape device)

The firefox-15.0.tar.bz2 archive can now be deleted.

3. Move to /opt

External programs like LibreOffice, Google Chrome, Adobe reader, ... are all installed in the /opt directory.

If you already had a previous Firefox version installed in the /opt directory, remove it with the following command:sudo rm -r /opt/firefox

of if you log as root user then use the following command

rm -r /opt/firefox

Now move the firefox directory (which was created in your Downloads folder during extraction) to /opt:sudo mv firefox /opt/firefox15

4. Set up symbolic linksCreate a symbolic link pointing to the new Firefox version:sudo ln -s /opt/firefox15/firefox /usr/bin/firefox

No need to update your icons/shortcuts, they should now launch the new version of Firefox.

Launch the newly installed Firefox by running firefox15 in a terminal, or create shortcuts/icons referring to firefox15.

5. Updates & Final

Firefox 15 will manage its own updates independently of your system's package manager, an download subsequent releases. There will be no need to repeat the whole “procedure”...